Turbofan engines generally comprise an annular bypass duct defined between radially outer and radially inner bypass duct walls. The inner bypass duct wall is typically attached to the engine core cases by means of sheet metal brackets. The brackets are bolted to core case flanges at one end and to the inner bypass duct wall at the other end. A first set of brackets may be mounted to the high pressure compressor case, a second set to the high pressure turbine case and a third set to the turbine exhaust case. The front end of the inner bypass duct wall is typically connected to the intermediate case of the engine core via a sliding joint, known as a “fishmouth” ring connection. This type of joint is used to allow the inner bypass duct wall to move axially and radially due to thermal growth with the engine core cases and, thus, reduce the amount of stress transferred to the brackets. However, it has been observed that the core cases and the brackets are subject to cracking problems as a result of the radial and axial thermal fight between the inner bypass duct wall and the engine core cases at the bracket locations.